1. Field of the Invention
The present invention relates to an apparatus for cleaning polymeric pieces. For instance, mold products of polymer such as thermoplastic resin (hereinafter referred to as “resin”) are collected and crushed or ground (hereinafter referred to as “crushed”) to be polymeric pieces. The present invention relates to an apparatus for cleaning such polymeric pieces for the purpose of re-using the same. More specifically, it relates to a cleaning apparatus for removing foreign matters from the polymeric pieces, such as coated or plated films applied to the surface of the polymeric mold products or labels or seals attached to the surface of the polymeric mold products or contaminant.
2. Description of the Related Art
At present, a large amount of various polymeric mold products have been used in a wide scope of use accompanied with the variety of life. There are various problems, however, in such variety of mold products after they have been used, as described below.
Most of the polymers have favorable features in resistance to water, resistance to weather or resistance to corrosion. However, a large amount of smoke and toxic gases are generated when the polymeric mold product is incinerated after being discarded, to contaminate the environment. Also, molten polymer may be adhered to a furnace wall to damage the incineration furnace. On the other hand, if they are buried under the ground, they remain unchanged for a long time without decay or decomposition to be one cause of the environmental disruption.
Also, since fossil resources itself which becomes raw material of polymer has been exhausted nowadays, it is required to reuse the used mold products without discarding the same.
The collected mold products, however, are often coated or plated with a film or applied with labels or seals or contaminated with various contaminant. Accordingly, there is a problem in that these foreign matters are mixed into the regenerated polymer during the regeneration treatment of the mold products to significantly deteriorate the properties of the obtained polymer. For this reason, at present, the polymer obtained from the collected mold products after the regeneration treatment is not generally used for the same utilization in which the polymer has been used before it is collected.
While various methods have been tried to remove the foreign matters from the surface of the molded product, such as a mechanical method or a solvent method, there are problems in either of them. For example, when the coated film or label is removed by using a crusher such as a ball mill, the polymer is softened due to the heat generated by friction during the crushing, resulting in the difficulty of removal of foreign matters or the re-adhesion of the foreign matters once removed. In the method in which the solvent is used for dissolving the foreign matters and separating the same, there is a problem in the regeneration or discarding of the used solvent, which requires a complicated structure of the apparatus used for the treatment and is uneconomical.
Another method for removing coated or plated film, label or others is a dry blast treatment in which abrasive material such as sand or metallic particle is used for scraping the foreign matters from the surface of the molded product. In this method, however, the abrasive material may bite into the surface of the polymeric mold product and remain there to form new foreign matters. Further, there is a problem in that polymer may be softened by the frictional heat of the abrasive material and the foreign matters once removed are adhered again thereto.